Independent specialists for me, just to keep the service book stamped.
But I do most stuff inbetween services.
I'd urge anyone to NOT use dealerships, my reasons being...
Toyota: Car returned to me 'ticking' after cambelt change, I returned it to the dealership to sort out.
Mazda: Cambelt snapped weeks after having been replaced by dealership, luckily it was a non-interference engine.
Mazda: Wheel nuts tightened so tight I couldn't undo them.
Toyota: Handbrake tightened so much that the rear brakes were permanently on.
Toyota: Sump plug worked lose and fell out 7 days after being serviced.
BMW/MINI: Took it upon themselves to wash my car and left TFR on the textured black paint of my Aero bumpers.